Determination of electron and hole lifetimes of rutile and anatase TiO2 single crystals

The dynamical behavior of photoexcited states of TiO2 governs the activities of TiO2-based solar cells and photocatalysts. We determined the lifetimes of photoexcited electrons and holes in rutile and anatase TiO2 single crystals by combining advantages of time-resolved photoluminescence, photoconductance, and transient absorption spectroscopy. Electrons and holes in rutile show exponential decays with the lifetime of a few tens of nanoseconds, while non-exponential decays are observed in anatase, indicating the presence of multiple carrier trapping processes. We revealed the generic features of the carrier recombination processes in rutile and anatase TiO2.